The present invention relates generally to window glazing units, and more particularly, to window glazing units comprising a shatter-resistant thermoplastic sheet positioned parallel to, and between two glass sheets.
Conventional double-paned window glazing units are frequently employed in construction due to their favorable insulating properties. Such double glazed windows have advantageous thermal insulating properties because a space exists between the two panes of glass. This space acts as a thermal barrier. Such windows have a serious drawback however, in that they remain susceptible to being easily broken.
Triple glazed windows are also know as described, for example in U.S. Pat. No. 5,553,440. Such windows may also be broken easily, particularly if all three sheets of glazing are glass. A further disadvantage of such units is that moisture may condense between the sheets of glazing. Moreover, such window units may fail if the panes are made from different materials, because the pane materials may differ in their coefficient of thermal expansion.
For the foregoing reasons, there is a need for a window glazing unit that is shatter resistant, is thermally efficient, is relatively light and which avoids developing water condensate between its panes. There is a further need for a bullet-resistant glazing having these same properties.